This invention relates generally to databuses of communications systems and communication networks, and more particularly to aircraft databuses.
It is common to link several computers or machines together so they can communicate with one another. A databus, or bus, is a communication channel along which data signals are transmitted between machines linked in a network. The databus may comprise one or more wires connected between various machines. If a databus is overloaded or subjected to outside influences, such as radiation, lightning, or other noise, the data signal may be disrupted or degraded, preventing or degrading its transmission.
On an aircraft, data signals from various computer systems for flight, navigation, communications, and other functions are often networked by a databus. Maintaining the integrity of data transmission over an aircraft databus is particularly important, because a failure can be disastrous. In addition, the failure of one computer system should not degrade the networking and operation of the other computer systems, and thus a firewall needs to be maintained on the aircraft.
Modern electronic communication systems operate at higher frequencies that are more susceptible to noise and other interference. A problem of prior art communication systems is that some systems, such as RS-422 standard systems, are not capable of handling high frequency signals. Other standard RS-485 systems do handle high frequency signals, but they can only transmit signals up to a maximum of 40 feet which is not long enough to cover the length of an aircraft fuselage from nose to tail, for example. Ethernet 10Base2 systems are susceptible to interference when exposed to High Intensity Radiated Fields (HIRF) because unbalanced signals are used. Attempts to minimize the HIRF effects in an Ethernet system are expensive and cumbersome because of the shielding and connectors required.
The present invention achieves technical advantages as an interface and method communicating data signals from an Ethernet DC unbalanced databus to a RS-485 compatible DC balanced databus. The present invention is a cost-effective interface system and method where signals are HIRF-resistant and transmittable up to lengths of 300 feet.
According to one embodiment, disclosed is a method of interfacing a DC unbalanced signal databus with at least one DC balanced signal databus using an interface system. The interface system has a controller coupled to a first transformer, which is coupled to a transmitter. The transmitter is a high power differential voltage driver and is coupled to a second transformer. The second transformer is coupled to the DC balanced databus, and signals are transmittable from the DC unbalanced signal databus to the DC balanced databus. The method comprises the steps of stepping up an alternating DC unbalanced voltage differential signal from the controller to a DC balanced voltage differential with the first transformer, and stepping up the DC balanced voltage differential signal from the first transformer to a high drive current signal with the transmitter. The second transformer isolates failures of the transmitter and the DC unbalanced bus from the DC balanced bus to maintain an aircraft firewall.
According to another embodiment, disclosed is an interface system for interfacing a DC unbalanced databus with at least one DC balanced databus, where the system comprises a DC unbalanced databus and a controller coupled to the DC unbalanced databus, wherein an alternating DC unbalanced voltage differential signal is transmittable from the controller. A first transformer is coupled to the controller, wherein the alternating DC unbalanced voltage differential signal may be stepped-up and DC balanced by the first transformer to create a DC balanced voltage differential signal. The system also comprises a transmitter coupled to the first transformer, where the transmitter is a high power differential voltage driver and where the DC balanced voltage differential signal may be stepped up by the transmitter to a high drive current signal. A second transformer is coupled to the transmitter, and at least one DC balanced databus is coupled to the second transformer.
Also disclosed is an interface system for bidirectionally interfacing a DC unbalanced databus. with at least one DC balanced databus, where the interface system is operable in a HIRF environment along extended distances. The system comprises a controller coupled to a DC unbalanced databus, where an alternating DC unbalanced voltage differential signal is transmittable from the controller. A first transformer is coupled to the controller, wherein the alternating DC unbalanced voltage differential signal may be stepped-up and DC balanced by the first transformer to create a DC balanced voltage differential signal. A transmitter is coupled to the first transformer, where the transmitter is capable of being disabled and also capable of being selectively tristated. The transmitter is a high power differential voltage driver, and the DC balanced voltage differential signal may be stepped up by the transmitter to a high drive current signal. A second transformer is coupled to the transmitter to provide a firewall between both the transmitter and DC unbalanced bus and the DC balanced databus. A receiver is coupled to the transmitter and the second transformer, where the receiver is capable of being disabled. A waveform shaping network is coupled to the second transformer, and at least one DC balanced databus is coupled to the second transformer. The receiver is coupled to the controller and the high drive current signal is retransmittable by the receiver to the controller.
The present invention offers technical advantages over conventional interface systems. The system and method provides a high-speed cost-effective HIRF-resistant interface system, where signals are transmittable up to 300 feet. Further advantages include low cost wiring connectors that are easy to assemble and the use of off-the-shelf components. Databuses are isolated so that failures on one part of the databus of the system do not cause failures on other parts of the databus.